Simultaneous RF electrical conductivity and topography mapping of smooth and rough conductive traces using microwave microscopy to identify localized variations

This paper presents a near-field microwave microscope (NFMM) capable of simultaneous non-contact imaging of electrical conductivity (σ) and topography across the surface of microwave circuits without the need of a distance sensor. The microscope monitors the resonant frequency of a dielectric resonator-based microwave probe to acquire the surface topography, and the quality factor to determine the electrical conductivity. Conductivity and topography images of copper foil reveal an average conductivity of about 4e7 S/m and an arithmetic roughness of 0.2μm, respectively. Measured average roughness and conductivity of CB028 silver paste are 0.7e6 S/m and 1.1μm, respectively. The NFMM data reveal significant and correlated variation in surface features and conductivity across the surface of the printed CB028 films. The topography and conductivity images obtained demonstrate that the NFMM can be employed for localized characterization of smooth and rough conductive materials used in microwave devices.